WASHINGTON — You probably think Roger Clemens used illegal performance-enhancing drugs during his career. I do, too. Based on what we know about the pitcher, his personality and his era, it makes sense.

It’s a common-sense conclusion, you might say.

But that’s just you and I talking. That’s not sufficient to throw Clemens in jail. Which is why the government raised eyebrows Tuesday as both sides presented their closing arguments in the U.S. v. Roger Clemens.

Repeatedly, Assistant U.S. Attorneys Gil Guerrero and Courtney Saleski invoked the notion of “common sense” in urging the jury to convict Clemens on all six counts of perjury, false statements and obstruction of Congress.

Which would be fine, if it weren’t wholly inaccurate. Sort of like the government’s attempt Tuesday to rehabilitate Andy Pettitte’s testimony.

As District Judge Reggie Walton instructed the jurors following the closing arguments, to convict, “It must be beyond a reasonable doubt. Reasonable doubt is a doubt based upon reason, evidence or lack of evidence in the case. If you cannot say you are firmly convinced of a defendant’s guilt, that is reasonable doubt.”

Clemens’ folksy, fiery lead attorney Rusty Hardin and his smooth associate Michael Attanasio, in the defense’s closing argument, offered plenty of fuel for reasonable doubt. They took joy in tearing down lead witness Brian McNamee, the former Yankees assistant strength coach, one more time. They pointed out the silliness many of the government’s lesser charges, such as Clemens’ assertion that he wasn’t at Jose Canseco’s house from June 8 through June 10 of 1998; as Attanasio said, “The government wants you to grade a spelling test, like in third grade.”

And they went over Pettitte’s testimony from May 2, in which Pettitte described as “fair” Attanasio’s assertion of a 50-50 likelihood that the Yankees’ left-hander misheard or misunderstood a 1999 or 2000 conversation with Clemens about illegal PEDs

The government’s spin of Pettitte’s words was just sad, like a fallen slugger trying to bunt his way on base. Since the prosecution touted Pettitte as one of its most important witnesses, only to see that blow up, Guerrero and Saleski were reduced to pleading with the jury to ignore the left-hander’s words from the cross-examination.

“You could see the tension in the courtroom [when Pettitte testified],” Guerrero said. “He didn’t want to testify against his friend. He was jumping at the chance to say it was 50-50.”

Well, first of all, they aren’t friends anymore. Moreover, if he was going to be such a lousy witness, then why did the government bother with him in the first place?

While Guerrero just hinted that Pettitte was not forthcoming, he went after Clemens’ wife, Debbie, with guns blazing, accusing her of lying about both the date and circumstances of her HGH shot from McNamee. It was Saleski’s responsibility, meanwhile, to explain away the damning testimony of McNamee’s wife, Eileen, expressing phony sympathy while describing Mrs. McNamee as being “all about self-preservation.”

To believe Clemens’ explanation of events, Saleski said, you’d have to digest “about a million coincidences, and that Roger Clemens unluckiest person in the world.”

Once more, though, the jury doesn’t have to believe anything Clemens’ attorneys threw out there. The burden of proof falls upon the prosecution, and while the government provided some food for thought with the testimony of McNamee — whom Guerrero described as “a flawed man” — and the science behind the needles (with steroids) and cotton balls (with Clemens’ DNA) he said he kept as protection, it hardly felt like enough.

Forever, we’ll discuss Clemens’ history and legacy and formulate our opinions. These 12 jurors have a different mission, however. Common sense or disbelief of the defense won’t get it done.

“You should be rewarding Roger Clemens, not prosecuting him,” a theatrical Hardin bellowed.

That’s a bit much. Yet the reward will come if the jury follows the court’s rules, ignores the government’s misleading advice and ends Clemens’ 54-month adventure with an acquittal.